Estimating in Building Construction

Concrete 99

FIGURE 10.13.Slab Areas.

FIGURE 10.14.Foundation Wall and Slab Detail.

FIGURE 10.15.Slab Area.

EXAMPLE 10-7 CONCRETE SLABS

The volume of a reinforced slab is found by taking the square
footage and by multiplying it by the depth of the slab. From the
drawings in Appendix A and Figures 10.13, 10.14, and 10.15, there
are four unique types of slabs. First, there is the 745 sf (25 3  31  4 
less 46 sf for stair opening) of 2-inch-thick topping.

Quantity of concrete (cy) 

The second slab is the 4-inch-thick slab that is in the front of the build-
ing. This slab is on grade and is 300 sf (30 feet 10 feet) and 4 inches
thick. Because the edges of this slab are thickened and it is on grade, a
larger waste factor will be used to compensate for this situation.

Quantity of concrete (cf )300 sf0.333¿100 cf

Quantity of concrete (cf )300 sf 4 –

Add 5% wasteUse 5 cy

127 cf>27 cf per cy4.7 cy

Quantity of concrete (cf )745 sf0.17¿127 cf

Third is the slab on grade for the remaining portion of the building

that is at grade. This area is found by determining the area for the

whole slab and by subtracting the 2-inch topping and 4-inch slab

by the front entrance, as shown in Figure 10.13.

The other remaining slab is the floor for the portion of the building

that is below grade. That takeoff is similar to the three previous

examples and can be found in Figure 10.16 with all the slab takeoffs.

Add 8 percent wasteUse 89 cy

Quantity of concrete (cy)2,214 cf>27 cf per cy82 cy

Quantity of concrete (cf )4,427 sf0.5¿2,214 cf

Add 8 percent wasteUse 4 cy

Quantity of concrete (cy)100 cf>27 cf per cy3.7 cy